ABSTRACT

Asthma in pregnancy is common, and its prevalence is rising. Internists need to be aware of the effects of maternal asthma control on the health of the expectant mother and the baby. With the ever-present worry about medication use and teratogenicity in pregnant women, these patients are often undertreated for their asthma. This review focuses on effects of uncontrolled maternal asthma as well as appropriate management of maternal asthma in the outpatient setting and during exacerbations.

KEY POINTS

The benefits of good adherence to asthma regimens during pregnancy outweigh the risks associated with the medications used.

For treatment of reflux disease in pregnant women with asthma, antacids (but not sodium bicarbonate, for fear of metabolic alkalosis) and sucralfate should be considered before a histamine 2 receptor antagonist such as ranitidine. Proton pump inhibitors should be considered only if reflux symptoms are refractory to other therapies.

The incidence of maternal asthma is rising. Based on US national health surveys, the prevalence of asthma during pregnancy is between 3.7% and 8.4%.1 It is the most common respiratory illness of pregnancy.2 Hence, clinicians need to know how asthma affects the mother and the fetus. Appropriate care of asthma during pregnancy is based on several management principles, as reviewed here, and is key to ensuring good outcomes for the mother and the baby.

EFFECT OF PREGNANCY ON ASTHMA CONTROL

Asthma control can vary in pregnancy. About a third of asthmatic women experience a worsening of asthma control with pregnancy, a third remain unchanged, and another third have improvement in asthma symptoms.3 The peak worsening of asthma tends to occur in the sixth month.4 Asthma control also tends to be better in the last month of pregnancy.3

The peak expiratory flow rate was noted to increase with each trimester in a small study of 43 women.5 The authors speculated that a rising progesterone level stimulates cyclic adenosine monophosphate to cause bronchodilation, thereby improving the expiratory flow rate and asthma control. Asthma control tends to follow the pattern experienced in the previous pregnancy: ie, if asthma worsened during the previous pregnancy, the same will be likely in the subsequent pregnancy.3

Two maternal factors that adversely affect asthma severity during pregnancy are the use of asthma medications contrary to guidelines such as those of the Global Initiative for Asthma (http://ginasthma.org/2017-gina-report-global-strategy-for-asthma-management-and-prevention) and inadquate control of asthma before becoming pregnant.6 Pregnancy can bring on stress, and stress is known to worsen asthma. In addition, when patients themselves were interviewed to elucidate the reasons for poor adherence to asthma medications during pregnancy, concerns about medication use, especially corticosteroids, stood out.7 A study based on prescription claims data showed that in the first trimester, there was a significant decline in asthma prescription medications (a 23% decline in inhaled corticosteroids, a 13% decline in short-acting bronchodilator agents, and a 54% decline in rescue corticosteroids).8 Lack of physician education about management of asthma in pregnancy and discomfort with prescribing to pregnant women also affect asthma control.

EFFECT OF ASTHMA ON MATERNAL AND FETAL OUTCOMES

Studies of the effects of asthma on fetal and maternal outcomes have yielded mixed and conflicting results.9 Adverse outcomes that have been shown to be associated with maternal asthma are listed in Table 1. Other studies have not demonstrated an association between asthma in pregnancy and maternal or fetal adverse events.9 Such discrepant findings are due to differences in study population characteristics that make comparisons difficult. A meta-analysis involving more than 1.6 million asthmatic women showed maternal asthma was associated with a 40% greater risk of low birth weight and preterm delivery, a 50% greater risk of preeclampsia, and a 20% greater risk of the baby being small for its gestational age.10

The association of maternal asthma and preterm birth may pose short-term and long-term health risks to the child associated with prematurity.9 Short-term risks with prematurity include infection, respiratory distress syndrome, brain injury, and necrotizing enterocolitis. Long-term risks include neuro­developmental and behavioral sequelae. Furthermore, asthma exacerbations during pregnancy are associated with a twofold higher risk of low birth weight.11 The benefits of good adherence to asthma regimens during pregnancy outweigh the risks associated with frequent symptoms and exacerbations caused by untreated asthma.12

OUTPATIENT MANAGEMENT OF MATERNAL ASTHMA

Goals

In the 2004 update of the National Asthma Education and Prevention Program (NAEPP) Working Group Report on Managing Asthma During Pregnancy, goals focused mainly on adequate asthma control for maternal health and quality of life, as well as normal fetal maturation (Table 2),12 goals similar to those in nonpregnant asthmatic women.

Assessment and monitoring

Monthly physician visits during pregnancy are recommended for assessment of symptoms and pulmonary function. If symptoms are uncontrolled, therapy must be stepped up, and any trigger for exacerbation, such as gastroesophageal reflux disease (GERD), exposure, or rhinitis, must be treated and eliminated. NAEPP guidelines recommend baseline spirometry at the time of initial assessment.12 At follow-up visits, spirometry is preferred, but measurement of the peak expiratory flow rate usually suffices. Such objective data can help differentiate dyspnea from asthma and from dyspnea that usually accompanies the physiologic changes of pregnancy. In addition, patients should be advised to monitor for adequate fetal activity. If asthma is uncontrolled or poorly controlled, serial fetal ultrasonography should be considered from 32 weeks of gestation, as well as after recovery from an asthma exacerbation. Regular monitoring of the pregnant asthmatic patient by a multidisciplinary team can improve outcomes.13